<?php
// vim: foldmethod=marker


/* Generic exception class
 */
class OAuthException extends Exception {
	// pass
}

class OAuthConsumer {
	public $key;
	public $secret;
	
	function __construct($key, $secret, $callback_url = NULL) {
		$this->key = $key;
		$this->secret = $secret;
		$this->callback_url = $callback_url;
	}
	
	function __toString() {
		return "OAuthConsumer[key=$this->key,secret=$this->secret]";
	}
}

class OAuthToken {
	// access tokens and request tokens
	public $key;
	public $secret;
	
	/**
	 * key = the token
	 * secret = the token secret
	 */
	function __construct($key, $secret) {
		$this->key = $key;
		$this->secret = $secret;
	}
	
	/**
	 * generates the basic string serialization of a token that a server
	 * would respond to request_token and access_token calls with
	 */
	function to_string() {
		return "oauth_token=" . OAuthUtil::urlencode_rfc3986($this->key) . "&oauth_token_secret=" . OAuthUtil::urlencode_rfc3986($this->secret);
	}
	
	function __toString() {
		return $this->to_string();
	}
}

/**
 * A class for implementing a Signature Method
 * See section 9 ("Signing Requests") in the spec
 */
abstract class OAuthSignatureMethod {
	/**
	 * Needs to return the name of the Signature Method (ie HMAC-SHA1)
	 * @return string
	 */
	abstract public function get_name();
	
	/**
	 * Build up the signature
	 * NOTE: The output of this function MUST NOT be urlencoded.
	 * the encoding is handled in OAuthRequest when the final
	 * request is serialized
	 * @param OAuthRequest $request
	 * @param OAuthConsumer $consumer
	 * @param OAuthToken $token
	 * @return string
	 */
	abstract public function build_signature($request, $consumer, $token);
	
	/**
	 * Verifies that a given signature is correct
	 * @param OAuthRequest $request
	 * @param OAuthConsumer $consumer
	 * @param OAuthToken $token
	 * @param string $signature
	 * @return bool
	 */
	public function check_signature($request, $consumer, $token, $signature) {
		$built = $this->build_signature($request, $consumer, $token);
		
		// Check for zero length, although unlikely here
		if (strlen($built) == 0 || strlen($signature) == 0) {return false;}
		
		if (strlen($built) != strlen($signature)) {return false;}
		
		// Avoid a timing leak with a (hopefully) time insensitive compare
		$result = 0;
		for ($i = 0; $i < strlen($signature); $i ++) {
			$result |= ord($built{$i}) ^ ord($signature{$i});
		}
		
		return $result == 0;
	}
}

/**
 * The HMAC-SHA1 signature method uses the HMAC-SHA1 signature algorithm as defined in [RFC2104] 
 * where the Signature Base String is the text and the key is the concatenated values (each first 
 * encoded per Parameter Encoding) of the Consumer Secret and Token Secret, separated by an '&' 
 * character (ASCII code 38) even if empty.
 *   - Chapter 9.2 ("HMAC-SHA1")
 */
class OAuthSignatureMethod_HMAC_SHA1 extends OAuthSignatureMethod {
	function get_name() {
		return "HMAC-SHA1";
	}
	
	public function build_signature($request, $consumer, $token) {
		$base_string = $request->get_signature_base_string();
		$request->base_string = $base_string;
		
		$key_parts = array(
			$consumer->secret, 
			($token) ? $token->secret : ""
		);
		
		$key_parts = OAuthUtil::urlencode_rfc3986($key_parts);
		$key = implode('&', $key_parts);
		
		return base64_encode(hash_hmac('sha1', $base_string, $key, true));
	}
}

/**
 * The PLAINTEXT method does not provide any security protection and SHOULD only be used 
 * over a secure channel such as HTTPS. It does not use the Signature Base String.
 *   - Chapter 9.4 ("PLAINTEXT")
 */
class OAuthSignatureMethod_PLAINTEXT extends OAuthSignatureMethod {
	public function get_name() {
		return "PLAINTEXT";
	}
	
	/**
	 * oauth_signature is set to the concatenated encoded values of the Consumer Secret and 
	 * Token Secret, separated by a '&' character (ASCII code 38), even if either secret is 
	 * empty. The result MUST be encoded again.
	 *   - Chapter 9.4.1 ("Generating Signatures")
	 *
	 * Please note that the second encoding MUST NOT happen in the SignatureMethod, as
	 * OAuthRequest handles this!
	 */
	public function build_signature($request, $consumer, $token) {
		$key_parts = array(
			$consumer->secret, 
			($token) ? $token->secret : ""
		);
		
		$key_parts = OAuthUtil::urlencode_rfc3986($key_parts);
		$key = implode('&', $key_parts);
		$request->base_string = $key;
		
		return $key;
	}
}

/**
 * The RSA-SHA1 signature method uses the RSASSA-PKCS1-v1_5 signature algorithm as defined in 
 * [RFC3447] section 8.2 (more simply known as PKCS#1), using SHA-1 as the hash function for 
 * EMSA-PKCS1-v1_5. It is assumed that the Consumer has provided its RSA public key in a 
 * verified way to the Service Provider, in a manner which is beyond the scope of this 
 * specification.
 *   - Chapter 9.3 ("RSA-SHA1")
 */
abstract class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {
	public function get_name() {
		return "RSA-SHA1";
	}
	
	// Up to the SP to implement this lookup of keys. Possible ideas are:
	// (1) do a lookup in a table of trusted certs keyed off of consumer
	// (2) fetch via http using a url provided by the requester
	// (3) some sort of specific discovery code based on request
	//
	// Either way should return a string representation of the certificate
	protected abstract function fetch_public_cert(&$request);
	
	// Up to the SP to implement this lookup of keys. Possible ideas are:
	// (1) do a lookup in a table of trusted certs keyed off of consumer
	//
	// Either way should return a string representation of the certificate
	protected abstract function fetch_private_cert(&$request);
	
	public function build_signature($request, $consumer, $token) {
		$base_string = $request->get_signature_base_string();
		$request->base_string = $base_string;
		
		// Fetch the private key cert based on the request
		$cert = $this->fetch_private_cert($request);
		
		// Pull the private key ID from the certificate
		$privatekeyid = openssl_get_privatekey($cert);
		
		// Sign using the key
		$ok = openssl_sign($base_string, $signature, $privatekeyid);
		
		// Release the key resource
		openssl_free_key($privatekeyid);
		
		return base64_encode($signature);
	}
	
	public function check_signature($request, $consumer, $token, $signature) {
		$decoded_sig = base64_decode($signature);
		
		$base_string = $request->get_signature_base_string();
		
		// Fetch the public key cert based on the request
		$cert = $this->fetch_public_cert($request);
		
		// Pull the public key ID from the certificate
		$publickeyid = openssl_get_publickey($cert);
		
		// Check the computed signature against the one passed in the query
		$ok = openssl_verify($base_string, $decoded_sig, $publickeyid);
		
		// Release the key resource
		openssl_free_key($publickeyid);
		
		return $ok == 1;
	}
}

class OAuthRequest {
	protected $parameters;
	protected $http_method;
	protected $http_url;
	// for debug purposes
	public $base_string;
	public static $version = '1.0';
	public static $POST_INPUT = 'php://input';
	
	function __construct($http_method, $http_url, $parameters = NULL) {
		$parameters = ($parameters) ? $parameters : array();
		$parameters = array_merge(OAuthUtil::parse_parameters(parse_url($http_url, PHP_URL_QUERY)), $parameters);
		$this->parameters = $parameters;
		$this->http_method = $http_method;
		$this->http_url = $http_url;
	}
	
	/**
	 * attempt to build up a request from what was passed to the server
	 */
	public static function from_request($http_method = NULL, $http_url = NULL, $parameters = NULL) {
		$scheme = (!isset($_SERVER['HTTPS']) || $_SERVER['HTTPS'] != "on") ? 'http' : 'https';
		$http_url = ($http_url) ? $http_url : $scheme . '://' . $_SERVER['SERVER_NAME'] . ':' . $_SERVER['SERVER_PORT'] . $_SERVER['REQUEST_URI'];
		$http_method = ($http_method) ? $http_method : $_SERVER['REQUEST_METHOD'];
		
		// We weren't handed any parameters, so let's find the ones relevant to
		// this request.
		// If you run XML-RPC or similar you should use this to provide your own
		// parsed parameter-list
		if (!$parameters) {
			// Find request headers
			$request_headers = OAuthUtil::get_headers();
			
			// Parse the query-string to find GET parameters
			$parameters = OAuthUtil::parse_parameters($_SERVER['QUERY_STRING']);
			
			// It's a POST request of the proper content-type, so parse POST
			// parameters and add those overriding any duplicates from GET
			if ($http_method == "POST" && isset($request_headers['Content-Type']) && strstr($request_headers['Content-Type'], 'application/x-www-form-urlencoded')) {
				$post_data = OAuthUtil::parse_parameters(file_get_contents(self::$POST_INPUT));
				$parameters = array_merge($parameters, $post_data);
			}
			
			// We have a Authorization-header with OAuth data. Parse the header
			// and add those overriding any duplicates from GET or POST
			if (isset($request_headers['Authorization']) && substr($request_headers['Authorization'], 0, 6) == 'OAuth ') {
				$header_parameters = OAuthUtil::split_header($request_headers['Authorization']);
				$parameters = array_merge($parameters, $header_parameters);
			}
		
		}
		
		return new OAuthRequest($http_method, $http_url, $parameters);
	}
	
	/**
	 * pretty much a helper function to set up the request
	 */
	public static function from_consumer_and_token($consumer, $token, $http_method, $http_url, $parameters = NULL) {
		$parameters = ($parameters) ? $parameters : array();
		$defaults = array(
			"oauth_version" => OAuthRequest::$version, 
			"oauth_nonce" => OAuthRequest::generate_nonce(), 
			"oauth_timestamp" => OAuthRequest::generate_timestamp(), 
			"oauth_consumer_key" => $consumer->key
		);
		if ($token)
			$defaults['oauth_token'] = $token->key;
		
		$parameters = array_merge($defaults, $parameters);
		
		return new OAuthRequest($http_method, $http_url, $parameters);
	}
	
	public function set_parameter($name, $value, $allow_duplicates = true) {
		if ($allow_duplicates && isset($this->parameters[$name])) {
			// We have already added parameter(s) with this name, so add to the list
			if (is_scalar($this->parameters[$name])) {
				// This is the first duplicate, so transform scalar (string)
				// into an array so we can add the duplicates
				$this->parameters[$name] = array(
					$this->parameters[$name]
				);
			}
			
			$this->parameters[$name][] = $value;
		} else {
			$this->parameters[$name] = $value;
		}
	}
	
	public function get_parameter($name) {
		return isset($this->parameters[$name]) ? $this->parameters[$name] : null;
	}
	
	public function get_parameters() {
		return $this->parameters;
	}
	
	public function unset_parameter($name) {
		unset($this->parameters[$name]);
	}
	
	/**
	 * The request parameters, sorted and concatenated into a normalized string.
	 * @return string
	 */
	public function get_signable_parameters() {
		// Grab all parameters
		$params = $this->parameters;
		
		// Remove oauth_signature if present
		// Ref: Spec: 9.1.1 ("The oauth_signature parameter MUST be excluded.")
		if (isset($params['oauth_signature'])) {
			unset($params['oauth_signature']);
		}
		
		return OAuthUtil::build_http_query($params);
	}
	
	/**
	 * Returns the base string of this request
	 *
	 * The base string defined as the method, the url
	 * and the parameters (normalized), each urlencoded
	 * and the concated with &.
	 */
	public function get_signature_base_string() {
		$parts = array(
			$this->get_normalized_http_method(), 
			$this->get_normalized_http_url(), 
			$this->get_signable_parameters()
		);
		
		$parts = OAuthUtil::urlencode_rfc3986($parts);
		
		return implode('&', $parts);
	}
	
	/**
	 * just uppercases the http method
	 */
	public function get_normalized_http_method() {
		return strtoupper($this->http_method);
	}
	
	/**
	 * parses the url and rebuilds it to be
	 * scheme://host/path
	 */
	public function get_normalized_http_url() {
		$parts = parse_url($this->http_url);
		
		$scheme = (isset($parts['scheme'])) ? $parts['scheme'] : 'http';
		$port = (isset($parts['port'])) ? $parts['port'] : (($scheme == 'https') ? '443' : '80');
		$host = (isset($parts['host'])) ? strtolower($parts['host']) : '';
		$path = (isset($parts['path'])) ? $parts['path'] : '';
		
		if (($scheme == 'https' && $port != '443') || ($scheme == 'http' && $port != '80')) {
			$host = "$host:$port";
		}
		return "$scheme://$host$path";
	}
	
	/**
	 * builds a url usable for a GET request
	 */
	public function to_url() {
		$post_data = $this->to_postdata();
		$out = $this->get_normalized_http_url();
		if ($post_data) {
			$out .= '?' . $post_data;
		}
		return $out;
	}
	
	/**
	 * builds the data one would send in a POST request
	 */
	public function to_postdata() {
		return OAuthUtil::build_http_query($this->parameters);
	}
	
	/**
	 * builds the Authorization: header
	 */
	public function to_header($realm = null) {
		$first = true;
		if ($realm) {
			$out = 'Authorization: OAuth realm="' . OAuthUtil::urlencode_rfc3986($realm) . '"';
			$first = false;
		} else
			$out = 'Authorization: OAuth';
		
		$total = array();
		foreach ( $this->parameters as $k => $v ) {
			if (substr($k, 0, 5) != "oauth")
				continue;
			if (is_array($v)) {throw new OAuthException('Arrays not supported in headers');}
			$out .= ($first) ? ' ' : ',';
			$out .= OAuthUtil::urlencode_rfc3986($k) . '="' . OAuthUtil::urlencode_rfc3986($v) . '"';
			$first = false;
		}
		return $out;
	}
	
	public function __toString() {
		return $this->to_url();
	}
	
	public function sign_request($signature_method, $consumer, $token) {
		$this->set_parameter("oauth_signature_method", $signature_method->get_name(), false);
		$signature = $this->build_signature($signature_method, $consumer, $token);
		$this->set_parameter("oauth_signature", $signature, false);
	}
	
	public function build_signature($signature_method, $consumer, $token) {
		$signature = $signature_method->build_signature($this, $consumer, $token);
		return $signature;
	}
	
	/**
	 * util function: current timestamp
	 */
	private static function generate_timestamp() {
		return time();
	}
	
	/**
	 * util function: current nonce
	 */
	private static function generate_nonce() {
		$mt = microtime();
		$rand = mt_rand();
		
		return md5($mt . $rand); // md5s look nicer than numbers
	}
}

class OAuthServer {
	protected $timestamp_threshold = 300; // in seconds, five minutes
	protected $version = '1.0'; // hi blaine
	protected $signature_methods = array();
	
	protected $data_store;
	
	function __construct($data_store) {
		$this->data_store = $data_store;
	}
	
	public function add_signature_method($signature_method) {
		$this->signature_methods[$signature_method->get_name()] = $signature_method;
	}
	
	// high level functions
	

	/**
	 * process a request_token request
	 * returns the request token on success
	 */
	public function fetch_request_token(&$request) {
		$this->get_version($request);
		
		$consumer = $this->get_consumer($request);
		
		// no token required for the initial token request
		$token = NULL;
		
		$this->check_signature($request, $consumer, $token);
		
		// Rev A change
		$callback = $request->get_parameter('oauth_callback');
		$new_token = $this->data_store->new_request_token($consumer, $callback);
		
		return $new_token;
	}
	
	/**
	 * process an access_token request
	 * returns the access token on success
	 */
	public function fetch_access_token(&$request) {
		$this->get_version($request);
		
		$consumer = $this->get_consumer($request);
		
		// requires authorized request token
		$token = $this->get_token($request, $consumer, "request");
		
		$this->check_signature($request, $consumer, $token);
		
		// Rev A change
		$verifier = $request->get_parameter('oauth_verifier');
		$new_token = $this->data_store->new_access_token($token, $consumer, $verifier);
		
		return $new_token;
	}
	
	/**
	 * verify an api call, checks all the parameters
	 */
	public function verify_request(&$request) {
		$this->get_version($request);
		$consumer = $this->get_consumer($request);
		$token = $this->get_token($request, $consumer, "access");
		$this->check_signature($request, $consumer, $token);
		return array(
			$consumer, 
			$token
		);
	}
	
	// Internals from here
	/**
	 * version 1
	 */
	private function get_version(&$request) {
		$version = $request->get_parameter("oauth_version");
		if (!$version) {
			// Service Providers MUST assume the protocol version to be 1.0 if this parameter is not present. 
			// Chapter 7.0 ("Accessing Protected Ressources")
			$version = '1.0';
		}
		if ($version !== $this->version) {throw new OAuthException("OAuth version '$version' not supported");}
		return $version;
	}
	
	/**
	 * figure out the signature with some defaults
	 */
	private function get_signature_method($request) {
		$signature_method = $request instanceof OAuthRequest ? $request->get_parameter("oauth_signature_method") : NULL;
		
		if (!$signature_method) {// According to chapter 7 ("Accessing Protected Ressources") the signature-method
// parameter is required, and we can't just fallback to PLAINTEXT
			throw new OAuthException('No signature method parameter. This parameter is required');}
		
		if (!in_array($signature_method, array_keys($this->signature_methods))) {throw new OAuthException("Signature method '$signature_method' not supported " . "try one of the following: " . implode(", ", array_keys($this->signature_methods)));}
		return $this->signature_methods[$signature_method];
	}
	
	/**
	 * try to find the consumer for the provided request's consumer key
	 */
	private function get_consumer($request) {
		$consumer_key = $request instanceof OAuthRequest ? $request->get_parameter("oauth_consumer_key") : NULL;
		
		if (!$consumer_key) {throw new OAuthException("Invalid consumer key");}
		
		$consumer = $this->data_store->lookup_consumer($consumer_key);
		if (!$consumer) {throw new OAuthException("Invalid consumer");}
		
		return $consumer;
	}
	
	/**
	 * try to find the token for the provided request's token key
	 */
	private function get_token($request, $consumer, $token_type = "access") {
		$token_field = $request instanceof OAuthRequest ? $request->get_parameter('oauth_token') : NULL;
		
		$token = $this->data_store->lookup_token($consumer, $token_type, $token_field);
		if (!$token) {throw new OAuthException("Invalid $token_type token: $token_field");}
		return $token;
	}
	
	/**
	 * all-in-one function to check the signature on a request
	 * should guess the signature method appropriately
	 */
	private function check_signature($request, $consumer, $token) {
		// this should probably be in a different method
		$timestamp = $request instanceof OAuthRequest ? $request->get_parameter('oauth_timestamp') : NULL;
		$nonce = $request instanceof OAuthRequest ? $request->get_parameter('oauth_nonce') : NULL;
		
		$this->check_timestamp($timestamp);
		$this->check_nonce($consumer, $token, $nonce, $timestamp);
		
		$signature_method = $this->get_signature_method($request);
		
		$signature = $request->get_parameter('oauth_signature');
		$valid_sig = $signature_method->check_signature($request, $consumer, $token, $signature);
		
		if (!$valid_sig) {throw new OAuthException("Invalid signature");}
	}
	
	/**
	 * check that the timestamp is new enough
	 */
	private function check_timestamp($timestamp) {
		if (!$timestamp)
			throw new OAuthException('Missing timestamp parameter. The parameter is required');
			
		// verify that timestamp is recentish
		$now = time();
		if (abs($now - $timestamp) > $this->timestamp_threshold) {throw new OAuthException("Expired timestamp, yours $timestamp, ours $now");}
	}
	
	/**
	 * check that the nonce is not repeated
	 */
	private function check_nonce($consumer, $token, $nonce, $timestamp) {
		if (!$nonce)
			throw new OAuthException('Missing nonce parameter. The parameter is required');
			
		// verify that the nonce is uniqueish
		$found = $this->data_store->lookup_nonce($consumer, $token, $nonce, $timestamp);
		if ($found) {throw new OAuthException("Nonce already used: $nonce");}
	}

}

class OAuthDataStore {
	function lookup_consumer($consumer_key) {
		// implement me
	}
	
	function lookup_token($consumer, $token_type, $token) {
		// implement me
	}
	
	function lookup_nonce($consumer, $token, $nonce, $timestamp) {
		// implement me
	}
	
	function new_request_token($consumer, $callback = null) {
		// return a new token attached to this consumer
	}
	
	function new_access_token($token, $consumer, $verifier = null) {
		// return a new access token attached to this consumer
	// for the user associated with this token if the request token
	// is authorized
	// should also invalidate the request token
	}

}

class OAuthUtil {
	public static function urlencode_rfc3986($input) {
		if (is_array($input)) {
			return array_map(array(
				'OAuthUtil', 
				'urlencode_rfc3986'
			), $input);
		} else if (is_scalar($input)) {
			return str_replace('+', ' ', str_replace('%7E', '~', rawurlencode($input)));
		} else {
			return '';
		}
	}
	
	// This decode function isn't taking into consideration the above
	// modifications to the encoding process. However, this method doesn't
	// seem to be used anywhere so leaving it as is.
	public static function urldecode_rfc3986($string) {
		return urldecode($string);
	}
	
	// Utility function for turning the Authorization: header into
	// parameters, has to do some unescaping
	// Can filter out any non-oauth parameters if needed (default behaviour)
	// May 28th, 2010 - method updated to tjerk.meesters for a speed improvement.
	//                  see http://code.google.com/p/oauth/issues/detail?id=163
	public static function split_header($header, $only_allow_oauth_parameters = true) {
		$params = array();
		if (preg_match_all('/(' . ($only_allow_oauth_parameters ? 'oauth_' : '') . '[a-z_-]*)=(:?"([^"]*)"|([^,]*))/', $header, $matches)) {
			foreach ( $matches[1] as $i => $h ) {
				$params[$h] = OAuthUtil::urldecode_rfc3986(empty($matches[3][$i]) ? $matches[4][$i] : $matches[3][$i]);
			}
			if (isset($params['realm'])) {
				unset($params['realm']);
			}
		}
		return $params;
	}
	
	// helper to try to sort out headers for people who aren't running apache
	public static function get_headers() {
		if (function_exists('apache_request_headers')) {
			// we need this to get the actual Authorization: header
			// because apache tends to tell us it doesn't exist
			$headers = apache_request_headers();
			
			// sanitize the output of apache_request_headers because
			// we always want the keys to be Cased-Like-This and arh()
			// returns the headers in the same case as they are in the
			// request
			$out = array();
			foreach ( $headers as $key => $value ) {
				$key = str_replace(" ", "-", ucwords(strtolower(str_replace("-", " ", $key))));
				$out[$key] = $value;
			}
		} else {
			// otherwise we don't have apache and are just going to have to hope
			// that $_SERVER actually contains what we need
			$out = array();
			if (isset($_SERVER['CONTENT_TYPE']))
				$out['Content-Type'] = $_SERVER['CONTENT_TYPE'];
			if (isset($_ENV['CONTENT_TYPE']))
				$out['Content-Type'] = $_ENV['CONTENT_TYPE'];
			
			foreach ( $_SERVER as $key => $value ) {
				if (substr($key, 0, 5) == "HTTP_") {
					// this is chaos, basically it is just there to capitalize the first
					// letter of every word that is not an initial HTTP and strip HTTP
					// code from przemek
					$key = str_replace(" ", "-", ucwords(strtolower(str_replace("_", " ", substr($key, 5)))));
					$out[$key] = $value;
				}
			}
		}
		return $out;
	}
	
	// This function takes a input like a=b&a=c&d=e and returns the parsed
	// parameters like this
	// array('a' => array('b','c'), 'd' => 'e')
	public static function parse_parameters($input) {
		if (!isset($input) || !$input)
			return array();
		
		$pairs = explode('&', $input);
		
		$parsed_parameters = array();
		foreach ( $pairs as $pair ) {
			$split = explode('=', $pair, 2);
			$parameter = OAuthUtil::urldecode_rfc3986($split[0]);
			$value = isset($split[1]) ? OAuthUtil::urldecode_rfc3986($split[1]) : '';
			
			if (isset($parsed_parameters[$parameter])) {
				// We have already recieved parameter(s) with this name, so add to the list
				// of parameters with this name
				

				if (is_scalar($parsed_parameters[$parameter])) {
					// This is the first duplicate, so transform scalar (string) into an array
					// so we can add the duplicates
					$parsed_parameters[$parameter] = array(
						$parsed_parameters[$parameter]
					);
				}
				
				$parsed_parameters[$parameter][] = $value;
			} else {
				$parsed_parameters[$parameter] = $value;
			}
		}
		return $parsed_parameters;
	}
	
	public static function build_http_query($params) {
		if (!$params)
			return '';
			
		// Urlencode both keys and values
		$keys = OAuthUtil::urlencode_rfc3986(array_keys($params));
		$values = OAuthUtil::urlencode_rfc3986(array_values($params));
		$params = array_combine($keys, $values);
		
		// Parameters are sorted by name, using lexicographical byte value ordering.
		// Ref: Spec: 9.1.1 (1)
		uksort($params, 'strcmp');
		
		$pairs = array();
		foreach ( $params as $parameter => $value ) {
			if (is_array($value)) {
				// If two or more parameters share the same name, they are sorted by their value
				// Ref: Spec: 9.1.1 (1)
				// June 12th, 2010 - changed to sort because of issue 164 by hidetaka
				sort($value, SORT_STRING);
				foreach ( $value as $duplicate_value ) {
					$pairs[] = $parameter . '=' . $duplicate_value;
				}
			} else {
				$pairs[] = $parameter . '=' . $value;
			}
		}
		// For each parameter, the name is separated from the corresponding value by an '=' character (ASCII code 61)
		// Each name-value pair is separated by an '&' character (ASCII code 38)
		return implode('&', $pairs);
	}
}